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Well-defined carbon nanoframes containing bimetal-N-C active sites as efficient bi-functional electrocatalysts for Li-Ch batterie

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Nano Research 2019年第3期12卷 517-523页

作者： Tie Liu Leidanyang Wang Tao huang Aishui Yu Department of Chemistry Collaborative Innovation Center of Chemistry for Energy Materials Institute of New Energy Fudan University Shanghai 200438 China Laboratory of Advanced Materials Fudan University Shanghai 200438 China

Design and fabrication of framework-structured porous precursors have been regarded as a prospective albeit challenging strategy to obtain bimetal/NC-enriched bifunctional elecrocatalysts. In this work, an effective bottom-up approach involving solution-based self-assembly and a post-annealing process was developed to confine (Co, Zn)-N-C active sites into N-enriched graphitic carbon nanocages. This novel architecture containing N-doped-C stabilized bimetallic nanoparticles derived from ZIF precursors was well-studied by a series of characterization and analysis techniques. Details were given that these well-dispersed (Co, Zn) nanoparticles were encapsulated into the pyridinic-N-dominated graphitic carbon nanocage with a total metal loading of approximately 7.4 at.%. This favorable hierarchical structure not only enhances the electron conductivity, but also owns a sufficient BET surface area facilitating the gas-liquid-solid triphase reaction and producing more space to store discharge products. Importantly, results infer that the interesting nanoframes manifests a satisfying ORR/OER activity and enhanced cell performance whether liquid or solid-state electrolytes are used. As such, our work rationalizes that this type of cage-shaped bimetal-N-C material is promising for high-performance Li-O2 batteries.

关键词： bifunctional electrocatalyst Li-oxygen battery nitrogen-doped carbon zinc-cobalt

Clocking Effect in a Two-Stage Compressor with Different Inter-Blade-Row Gaps

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Journal of Thermal Science 2004年第1期13卷 8-15页

作者： Hongyan huang Haitao Yang Guotai Feng Zhongqi Wang Harbin Inst Technol Harbin 150001 Peoples R China

A multi-stage axial compressor has inherently unsteady flow fields because of the following main reasons: (1) relative positions between rotor and stator airfoil; (2) the buildup of converted wakes lead to complex wake/wake and wake/airfoil interactions. The distributions of the potential flows and wakes in the flow passage are depended on the relative positions of blade rows in axial and circumference direction, so variations in the relative axial positions (axial gap) and circumferential positions (clocking effect) of stators or rotors can change these distributions, leading to different compressor efficiency. The current study presents the experimental/numerical result of a low-speed axial compressor, considering the combined effects of stator clocking and variation of axial gaps. Testing was conducted in Two-Stage Axial Compressor Facility in Harbin Institute of Technology. In the test, time averaged data were collected. The results of experimental and time accurate flow calculation for 2 axial gaps, 8 clocking positions for each gap are compared. It is shown that clocking determines the degree of interaction of a stator with the wake of another upstream stator for different gaps between the blade rows.

关键词： clocking compressor gap wake loss.

Theoretical analysis of the convergence property of a basic pigeon-inspired optimizer in a continuous search space

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Science China(Information Sciences) 2019年第7期62卷 90-98页

作者： Yushan ZHANG Han huang Hongyue WU Zhifeng HAO School of Statistics and Mathematics Guangdong University of Finance and Economics Big Data and Educational Statistics Application Laboratory Guangdong University of Finance and Economics School of Software Engineering South China University of Technology School of Mathematics and Big Data Foshan University

The pigeon-inspired optimization(PIO) algorithm is a newly presented swarm intelligence optimization algorithm inspired by the homing behavior of pigeons. Although PIO has demonstrated effectiveness and superiority in numerous fields, particularly in practical engineering optimization, there have been few results concerning the theoretical foundations of PIO. This paper conducts convergence analysis of basic PIO in a continuous search space in two aspects. First, we analyze the convergence of each pigeon’s expected position using a difference equation and prove that the average position of each pigeon in the swarm will converge to the same value. To further study the stochastic global convergence property of the pigeon swarm, we apply the martingale theory to investigate the basic PIO swarm sequence, and achieve a sufficient condition to guarantee global convergence of the basic PIO. Our theoretical analysis shows that this convergence depends upon the accumulation of the minimum probability with which the pigeon swarm jumps to the global-optimal region at each iteration. The mathematical methods proposed in this study, particularly the martingale technique, also provide a new effective approach for the theoretical analysis of bio-inspired algorithms in continuous optimization.

关键词： pigeon-inspired optimization(PIO) convergence analysis martingale continuous optimization swarm intelligence

Stability analysis of high power factor Vienna rectifier based on reduced order model in d-q domain

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Journal of Modern Power Systems and Clean Energy 2019年第1期7卷 200-210页

作者： Chaoliang DANG Xiangqian TONG Weizhang SONG Jingjing huang Department of Electrical Engineering Xi'an University of Technology

For a DC distributed power system, system stability can be predicted by dividing it into source and load subsystems, and then applying the Nyquist criterion to the impedance interaction between the source and load ***, the generalized Nyquist criterion is extremely complicated and cannot directly reveal effective control strategies to reduce interaction problems of cascade threephase AC ***, as a current force rectifier,this characteristic makes it difficult to judge the stability of a cascade three-phase Vienna AC *** deal with the aforementioned problems, a simplified small signal stability criterion is presented for an AC distributed power *** on the criterion, the small signal model and impedance based on the reduced order model in the dq domain are studied *** the instability issue,an impedance regulator design method is *** correctness of the simplified stability criterion and the effectiveness of the proposed impedance regulator method are validated by extensive simulation and experiment.

关键词： Three-level Vienna rectifier Small-signal stability Nyquist criterion Grid impedance Impedance regulator

Experimental study of a controlled variable double-baffle distortion generator engine test rig

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Chinese Journal of Aeronautics 2018年第9期31卷 1880-1893页

作者： Aiguo XIA Xudong huang Wei TUO Ming ZHOU School of Aerospace Engineering Tsinghua University Beijing Aeronautical Technology Research Center

In order to explore the total-pressure distortion test assessment method for a turbofan engine, a Controlled Variable Double-Baffle Distortion Generator(CVDBDG) with a horizontal symmetry moving form was developed, which can adjust the steady-state and time–variant distortion separately in real time. The inlet total-pressure distortion test was conducted on an afterburner turbofan engine. The distortion parameters of CVDBDG and the instability characteristics of the engine were measured. The experimental data were modeled and analyzed by using back propagation artificial neural networks, and the work envelope of CVDBDG was obtained. Based on the analysis of the data on the engine’s instability, the properties of CVDBDG used for the stability assessment were preliminarily evaluated. The results show that CVDBDG can simulate both steady-state and time–variant distortions simultaneously in a range determined by three *** the condition of symmetric double baffles, a critical depth of insertion exists, beyond which the symmetric baffles will generate an asymmetric flow field. In the case of double baffles, compared to a single baffle, the engine exhibited different instability characteristics. Based on CVDBDG, it is expected that more efficient engine stability and durability assessment methods can be developed.

关键词： Distortion generator Engine stability Inlet flow Inlet total-pressure distortion Turbofan engines

Adaptive Data Wiping Scheme with Adjustable Parameters for Ext4 File System

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Chinese Journal of Electronics 2017年第2期26卷 392-398页

作者： ZHANG Peng NIU Shaozhang huang Zhenpeng QIN Xiaohua Beijing Key Laboratory of Intelligent Telecommunication Software and Multimedia Beijing University of Posts and Telecommunications School of Physics Electrical Engineering Ningxia University

Data wiping is a useful technology which can prevent possible data recovery in a file *** the growth of the amount of data usually leads to a decline in wiping *** order to make improvement,a novel data wiping scheme for Ext4 file system DWSE is *** includes two proposed algorithms for wiping files and free space *** to a rate of rest blocks which is specified by users,the file wiping algorithm WFile tries to clean part of a selected file for saving *** free space wiping algorithm WFree tries to speed up the process of cleaning dirty blocks by employing a random sampling and hypothesis testing method with two adjustable rates which represent status and content of a block group.A journal cleaning algorithm Clean J is also proposed which tries to clean old records by creating and deleting temporary files for preventing data recovery from a journal *** the help of parameters,users can wipe their data in a balanced way between security and *** experiments are performed on our *** experimental results show that our scheme can wipe files and free space in different security and efficiency with different *** scheme can achieve higher security and efficiency than other two data wiping schemes.

关键词： Data wiping Adjustable parameters Ext4 Random sampling Hypothesis testing

Modified Frequency Scaling Algorithm for FMCW SAR Data Processing

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Chinese Journal of Aeronautics 2007年第4期20卷 339-345页

作者： Jiang Zhihong huang Fukan Wan Jianwei Cheng Zhu College of Electronic Science and Engineering National University of Defense Technology Changsha 410073 China

This paper presents a modified frequency scaling algorithm for frequency modulated continuous wave synthetic aperture radar （FMCW SAR） data processing. The relative motion between radar and target in FMCW SAR during reception and between transmission and reception will introduce serious dilation in the received signal. The dilation can cause serious distortions in the reconstructed images using conventional signal processing methods. The received signal is derived and the received signal in range-Doppler domain is given. The relation between the phase resulting from antenna motion and the azimuth frequency is analyzed. The modified frequency scaling algorithm is proposed to process the received signal with serious dilation. The algorithm can effectively eliminate the impact of the dilation. The algorithm performances are shown by the simulation results.

关键词： FMCW radar SAR radar imaging frequency scaling algorithm

Mechanism analysis of foam penetration in EPB shield tunnelling with a focus on FER and soil particle size

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Underground Space 2024年第4期17卷 170-187页

作者： He huang Quan Sun Tao Xu Wanhuan Zhou State Key Laboratory of Internet of Things for Smart City and Department of Civil and Environmental Engineering University of MacaoMacao 999078China Department of Civil and Environmental Engineering University of MacaoMacao 999078China School of Transportation Southeast UniversityNanjing 210000China

Parameters of foam penetration in earth pressure balance(EPB)shield tunnelling,such as permeability coefficients and penetration distances,significantly impact tunnel face ***,existing studies have faced inaccuracies in analysing these parameters due to imitations in experimental *** study addresses this issue by employing enhanced methods for a more precise analysis of foam *** involving three distinct sand types(coarse,medium,and fine)and three foam expansion ratios(FER)(10,15,and 20)are conducted using a modified model test *** from a novel computer vision-based method,the model test outcomes unveil two distinct foam penetration paths:liquid migration(L_(w))and bubble migration(L_(f)).Three penetration phases-namely,injection,blockage&drainage,and breakage—are identified based on L_(w)and L_(f)*** initial"injection"phase conforms to Darcy’s law and is amenable to mathematical *** foam with FER of 15 has the maximum viscosity and,hence the L_(f)and permeability in the penetration tests with FER of 15 are the lowest in the same *** bubble size distribution of foam with different FER shows minor ***,the characteristics of foam penetration vary due to the distinct particle size distribution(PSD)of different *** penetration creates low-permeability layers in both medium and fine sands due to the larger bubble size of the foam compared to the estimated pore sizes of medium and fine *** the coarse sand results in a different situation due to its large pore *** distinctive characteristics of foam penetration in different sand strata are notably shaped by FER,PSD,and pore size *** insights shed light on the complex interactions during foam penetration at the tunnel face,contributing valuable knowledge to EPB shield tunnelling practices.

关键词： EPB Soil conditioning Foam penetration Permeability Tunnel face

Efforts towards Practical and Sustainable Li/Na-Air Batteries

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Chinese Journal of Chemistry 2021年第1期39卷 32-42页

作者： Kai Chen Gang huang Xin-Bo Zhang State Key laboratory of Rare Earth Resources Uiliation Changchun Institute of Applied ChemistryChinese Academy of SciencesChangchunJilin 130022China University of Science and Technology of China HefeiAnhui 230026China Materials Science and Engineering Physical Science and Engineering DivisionKing Abdullah University of Science and Technology(KAUST)Thuwal23955-6900Saudi Arabia

The Li-O_(2) batteries have ttrcted much attention due to their parallel theoretical energy density to *** the past 20 years,understanding and knowledge in Li-O_(2) battlry have greatly deepened in elucidat-ing the relationship between structure and *** group has been focusing on the cathode en-gineering and anode protection strategy development in the past years,trying to make full use of the supe-riority of metal-air batteries towards *** this review,we aim to retrospect our efforts in devel-oping practical,sustainable metal-air *** will first introduce the basic working principle of Li-O_(2) batteries and our progresses in L-O_(2) batteries with typical cathode designs and anode protection strategies,which have together promoted the large capacity,long life and low charge *** emphasize the designing art of carbon-based cathodes in this part along with a short talk on all-metal *** fol-lowing part is our research in Na-O2 batteries including both cathode and anode *** differ-ences between Li-O2 and Na-O2 batteries are also briefly ***,our proof-of-concept work on Li-N2 battery,a new energy storage system and chemistry,is discussed with detailed information on the discharge product ***,we summarize our designed models and prototypes of flex-ible metal-air batteries that are promising to be used in flexible devices to deliver more power.

关键词： Energy conversion Mesoporous materials Anode protection Flexible batteries Li-N_(2)batteries